The invention relates to an ultrasonic image processing method for displaying an ultrasonic examination color-coded image sequence of an object having moving parts in a medium. The invention also relates to an ultrasonic examination imaging system for carrying out this method.
The invention is used in the field of ultrasonic diagnostic imaging, for providing cardiovascular non-invasive diagnostic tools for studying anomalies of arteries and notably stenoses. A basic diagnostic criterion for a stenosis is an abrupt reduction of the diameter of a suspect artery segment observed in an artery image. A more elaborate criterion is the study of the artery wall displacements in function of the instants of the cardiac cycle and in function of the location along the artery segment. Therefore, in order to early diagnosing stenosed arteries, the medical field has a need for non-invasive means for providing artery images together with readily visible indications related to the arterial wall displacements.
An ultrasonic image processing method for calculating wall displacements of an artery segment is already known from the patent U.S. Pat. No. 5,579,771 (Bonnefous, Dec. 3, 1996). This document describes a method for characterizing an artery segment by ultrasonic imaging, using an array of ultrasonic transducers that produces a sectional frame, which is formed by image lines of a number of successive parallel excitation lines extending perpendicularly to the artery axis. Said array is coupled to a transmitter/receiver circuit, which provides high frequency signals to a signal processing system. Said system determines the arterial wall velocities and displacements, in the arterial radial direction Z, at a given location corresponding to an excitation line along the longitudinal X-axis of the artery, in function of excitation instants t, during a cardiac cycle. So, FIG. 1 of this document shows a system in a block diagram form, apt to carry out this method.
So, under the influence of the pulsating wave of the blood in the artery during a cardiac cycle, the walls of the artery are subject to periodic radial movements whose amplitude and velocity can be determined. Depending on the state of the arterial walls, the pressure variations induced by the pulsating wave create either a uniform arterial dilatation or distorted parietal movements. Evaluating the distortions or non-distortions of the artery walls permits of deriving the presence and seriousness of stenosis, or elasticity defects, in real time, enabling optimization of the diagnosis. To that end, it is important to obtain information about the arterial wall movements and it is still more important to obtain information about the wall movement variations, i.e the movement gradients.
So, a problem lies in the fact that the movement gradients are not readily exploitable by a cardiologist. Not only the arterial wall movement variations must be made easily available and exploitable, but also, concomitantly, a standard grayscale image of the corresponding artery segment must be displayed, in order to perform a successful study and a precise diagnosis of the suspect zone of artery.
Now, a further problem lies in the fact that the gradient information, which is to be further added to the grayscale image, must not make this grayscale image unreadable.
The problems discussed above are solved by means of a method as disclosed herein.
An advantage of the method of the present embodiments is that the arterial wall behavior is made clearly visible together with the gradient information that is strongly related to arterial wall lesions. This is most useful to establish a diagnosis. Another advantage is that non-invasive means are used, which permit avoiding a modification of the artery pressure, hence the actual wall movements, as would be the case using invasive means.
An ultrasonic diagnostic system having means for carrying out the method is also disclosed.